heat treat old nicholson file never got straw color,

V

VII Blades

Joined
Dec 13, 2011
Messages
11
I just finished up my 2nd batch of old nicholson file knives and after I heated to above non magnetic, oil quenched, then allowed to cool to about 150 I put the blades in the oven at 450 to temper to a 59 ish. I baked them for 2 hours two times. They came out with a slight blue tinge, which worried me. But everywhere I check says you can heat to 500 and still be above a 58. Am I just not cleaning up the blades good enough after the quench?
 
Sounds like your oven might be a little hot. Are you using your kitchen oven to temper? They can swing through 50 degrees F (and more) to maintain temperature. I place mine on a cookie sheet to protect from direct influence of the element.


-Xander
 
Go buy you an oven thermometer from some place like Wallyworld, it is not uncommon for the temp settings to be of 25-50* for a home oven. The thermometer will allow for outside monitoring and then you can readjust your setting to match.
 
Don't try to judge temper by color,left over oil residue and other contaminants can very the colors.Get a oven thermometer and go by temp.
Stan
 
SBuzek said:
Don't try to judge temper by color,left over oil residue and other contaminants can very the colors.Get a oven thermometer and go by temp.
Stan
Click to expand...

This. Even if you scrub them good, there's still a little bit of quench oil on the blades. Can't trust colors unless you go down to bare steel, but no point in doing that if you have a thermometer.
 
As everyone has said get another thermometer. I also place a cast iron griddle in the oven to help stabilize the temp. I do clean them before putting in the oven - stinks up the place if I don't........steve
 
Thanks guys. I have a thermometer, but it is a cheap one, but it seemed to be right on. And the temp would have to be off 100 degrees for the blue to appear I imagine and I know that can't be the case. 50 degrees off would still leave the knives around 58, so if that were the case I am still fine. I will definatly try the skillet to regulate the temp.
 
For what it's worth, when I temper blades in my kitchen-based tempering oven ;-) I pre-heat it to the temp I want. The blades are on a cookie sheet and are held on their spines by some holders I made from cut up steel cans, and I put a loose tent of aluminum foil over them to keep the radiant heat off the blades when the heating element cycles on and off. The idea of adding a cast iron frying pay for thermal mass is a good one. Unfortunately I got rid of mine when I got a smooth glass top stove.

- Paul Meske
 
You must log in or register to reply here.
Back
Top